In general, the present invention is situated in the context of neuroprostheses, and in particular is closely related to cochlear implants adapted for treatment of hearing loss in situations where conventional hearing aids cannot be used to sufficiently restore the auditory function of the patient but where the patient's auditory nerve is still operational. Specifically, cochlear implants are very advanced medical devices that transform speech, i.e., sound waves, into electrical current signals which are delivered, by bypassing malfunctioning or damaged structures of the ear, directly to the auditory nerve of deaf patients. Stimulated in such way, the auditory nerve then sends these artificial signals to the brain which recognizes them as sound, allowing the restoration of some auditory perception. The results are quite impressive, allowing for example post-lingually deafened, implanted adults to make use again of telephones or pre-lingually deafened, sufficiently early implanted children to develop oral language as their principal means of communication and attend normal schools with their hearing peers.
Cochlear implants now have a successful clinical history of more than 25 years with more than 300,000 implanted patients worldwide. Therefore, these devices nowadays can be considered to be very reliable, whilst for other medical applications requiring implantable functional electrical stimulators of neural or muscular tissue corresponding devices with similar reliability and well proven functionality currently do not exist.
Nevertheless, there have been efforts to realize similar devices for use as neuroprostheses in other medical applications like the restoration of the vestibular function of patients with balance disorders. Such systems need to capture the motion of the head of the patient via motion sensors like gyroscopes and/or accelerometers and to output a pattern of electrical impulses adapted to stimulate the different branches of the vestibular nerve.
Examples of such approaches are disclosed, amongst others, in documents WO2012/012634 describing a vestibular implant system with internal and external motion sensors, U.S. Pat. No. 7,647,120 describing a dual cochlear/vestibular stimulator, and WO2010/135783 describing a vestibular stimulation array of electrodes specifically adapted for implantation in a semicircular canal of the vestibular system, all of which are incorporated herein by reference in their entireties. These documents also comprise some general explanations on the anatomy of the human ear and the background of cochlear and vestibular sensory loss as well as the ability of known devices to restore such loss, most of this information thus not being repeated at this place for the sake of conciseness.
In particular, WO2012/012634 concerns the difficulties that face efforts to realize vestibular implants already on the level of the different kind of sensors required, namely motion sensors the position of which needs to be well determined and stable relative to the head of the patient, as compared to a relatively simple microphone used as speech sensor for cochlear implants. To optimize this aspect, WO2012/012634 proposes both internal, i.e., implanted, and external motion sensors attached to the patient's head by means of specially configured magnets.
The document U.S. Pat. No. 7,647,120 proposes a device adapted for both restoration of the auditory—and the vestibular function, since some patients suffer disorders of both of these functions. For that purpose, the proposed device comprises both a speech processor and a motion processor treating the signals from the corresponding sensors, i.e., from a microphone, respectively from the motion sensors. However, such a device necessarily is more voluminous and complicated as compared to a cochlear implant. The volume, of course, is critical for any device supposed to be, at least partially, implanted. Even more importantly, the presence of a motion processor specifically designed to treat signals from motion sensors necessitates quite important research and development and represents a potential risk on the level of the secure operation of the device as compared to the existing speech processors the performance and reliability of which are proven by years of clinical use. If fact, since vestibular implants are aimed at treatment of patients suffering from chronic disequilibrium and oscillopsia, i.e., movement of the visual field during movement of their head, malfunctioning of the implant risks to directly affect the patient's general health and security, for example because the latter could fall in case the vestibular implant fails to work correctly.
The document WO2010/135783 concerns the issue of disposing of an array of electrodes specifically adapted for implantation in a semicircular canal of the vestibular system whilst simultaneously avoiding damage to anatomical structures of the ear. For this purpose, an array of electrodes is proposed where each electrode is dimensioned and constructed such as to preserve residual vestibular function, in particular without substantially compressing the membranous labyrinth.
However, whilst the above mentioned devices and corresponding methods, like others not having been mentioned explicitly, contribute to the developments having been achieved in recent years in the field of vestibular implants, several drawbacks and problems still remain. First, electrical stimulation of neural and/or muscular tissue is required also for several other medical applications, not just for restoration of the auditory—and the vestibular function. Each of these medical applications has some specific requirements but potentially also some overlap with applications already under study since a long time, like restoration of the auditory function using cochlear implants. Such overlap could allow to use to some extent proven technology which is not fully exploited by prior art devices. Second, the development of processors specifically and almost entirely redesigned to treat signals from the specific sensors required for the given medical application represents an obstacle to rapid development as well as a potential risk for the patient, like mentioned above in the case of vestibular implants comprising a newly designed motion processor adapted to treat signals of motion sensors. Other medical applications which require a similar device adapted to be used as functional electrical stimulators are for example retinal implants, heart pacemakers, devices for functional electrical stimulation in neurological disorders such as Parkinson, etc. In most of these cases, there currently do not exist specifically adapted devices having a similar reliability and well proven functionality as compared to cochlear implants for the restoration of audition.
It is thus the object of the present invention to overcome the above mentioned difficulties and to realize a device for electrical stimulation of neural tissue adapted to be used in several medical applications. It is another objective of the present invention to extend the use of very precise, proven, and readily available medical technology like cochlear implants to a variety of related medical applications requiring electrical stimulation of neural tissue. Another objective of the present invention consists in reducing development time and cost for such devices whilst increasing the level of reliability of these devices and thus enhancing the patient's security.
To this effect, the present invention proposes a device, which is characterized by the features enumerated in the claims and which allow to achieve the objectives identified above, respectively a corresponding method according to the claims.
In particular, the device, respectively the corresponding method, according to the present invention is characterized by the fact that the device, next to comprising a known cochlear implant and at least another signal sensor, further comprises a signal transformation unit, said signal sensors being adapted to capture relevant input information and to deliver a corresponding input signal to the transformation unit, the latter allowing to transform said input signal received from the signal sensors into a modulated electrical output signal adapted to be treated by the speech processor of the cochlear implant.
More particularly, the transformation unit of such a device comprises a waveform generator adapted to generate an acoustic carrier waveform of a given frequency, at least an input allowing each for introduction of an input signal from a corresponding signal sensor connected to said input, a first amplifier allowing to amplify the signal of the acoustic carrier waveform, a third amplifier allowing to amplify the input signal, and a signal modulation component allowing to modulate in amplitude the acoustic carrier waveform generated by the waveform generator by the input signal as well as an output allowing to deliver an amplitude modulated output signal to the speech processor of the cochlear implant.
Therefore, in sum, a device, respectively a method according to the present invention allow to transform an input signal received from a large variety of signal sensors into an amplitude modulated output signal which is adapted to be treated by the speech processor of known cochlear implants, thus allowing to extend the usability of these proven devices to a variety of medical applications.
Other features and advantages of the present invention are mentioned in the dependent claims as well as in the description disclosing in the following, with reference to the figures, the invention in more detail.